Supplementary Figure 5: Cation binding in PC2 and comparison of the presumed open states to the closed PC2_CL.

(a) Ca²⁺ (green spheres) and potential other cations (blue spheres) in PC2_MI aligned with Ca²⁺ in Ca_VAB (yellow spheres, pdb entry code 4MVO) and TRPV6 (magenta, pdb entry code 5IWP). Gray spheres indicate the position of cations in PC2_SI. (b) Spatial constraints in the translocation pathway of PC2 states with Ca_VAB (magenta, pdb entry code 4MVO). Radii along the translocation pathway of PC2_MI (green) and PC2_SI (blue) were calculated using the script HOLE. Residues forming narrow constrictions are indicated. Structural difference between PC2_MI, PC2_SI and the closed state PC2_CL (Grieben et al., 2016): c) PC2_MI and d) PC2_SI are shown as worm models; colors and channel diameters indicate C_α r.m.s.d. relative to PC2_CL (blue 0 Å, white 1.5 Å and red >3 Å, larger diameter stands for larger deviation; C_α of PC2_CL is shown as black wire).